Although your symptoms are quite vague and general, the most likely possibilities would be:-Hypothyroidism-Diabetes-Cardiac conditions-Kidney disorders

In my opinion a full check-up would certainly help you ma'am. But if you do not intend on going for this, the specific investigations you would have to go about are:-Thyroid profile (blood sample required)-Glycaemic (blood sugar) profile [blood sample required]-12 lead ECG (EKG) test-Renal function tests (blood sample required)

As you already have mentioned diabetes, we will have to rule out other causes to conclude that these changes are due to diabetes. If diabetes is found to be the cause, regular monitoring of your blood sugar levels will be required, as your symptoms match that of low blood sugar levels (hypyglycemia) which could be due to various reasons like excessive medication, exercise, poor diet, etc. You will have to get your blood sugar levels checked while/during you experience your above symptoms.

I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications. I would gladly help you.